Effect of processed sweet lupin (Lupinus angustifolius) grain supplementation on growth performance and socioeconomic feasibility of Doyogena sheep in Ethiopia

Abstract Background The experiment evaluated the effect of supplementing sheep fed natural pasture hay withprocessed sweet lupin grain on growth performance and its economic feasibility. The finding revealed that use of steamed lupin shown to improve the nutritivevalue of the grain and sheep performance. Methods The experiment was carried out using 24 yearling lambs with initial body weight of 27.53 ± 2.67 kg (mean ± SD) for 126 days (21 days quarantine, 15 days of adaptation and 90 days growth trial followed by 7 days digestibility trial). The experiment was laid out in a randomised complete block design consisting of four treatments and six blocks. Treatments comprised the feeding of natural pasture hay ad libitum + concentrate mix 440 g (T1), natural pasture hay + 440 g/day roasted, coarsely ground sweet lupin grain (T2), natural pasture hay + 440 g/day sweet lupin grain soaked in water for 72 h (T3), natural pasture hay + 440 g/day steamed sweet lupin grain (T4). Results There was improvements in total dry matter intake and digestibility coefficients of dry matter, organic matter, crude protein, neutral detergent fibre and acid detergent fibre in sheep supplemented with processed sweet lupin grains compared (T4) by 58.49%, 24.66%, 39.39%, 22.97% and 39.68%, respectively, over the control group. Specifically sheep supplemented with T4 had significantly higher (p < 0.001) average daily gain (by 51.04%), feed conversion efficiency (46.34%) and daily weight gain (144.78 g/day) compared to the control treatment, respectively. All processing methods resulted in favourable average daily gain and net return, thus can be employed in feeding systems depending on their availability and relative cost. Conclusions Supplementing sheep fed natural pasture hay with 440 g/day steamed sweet lupin grains improved growth performance and fattening economics of Doyogena sheep compared to T2 (roasted sweet lupin grain), T3 (soaked sweet lupin grain) or the control (T1).


K E Y W O R D S
growth performance, processed sweet lupin grain, sheep INTRODUCTION In Ethiopia, the livestock sub-sector has a significant contribution to the national income and livelihoods of households (Leta & Mesele, 2014). However, the role of the sector towards the country's economy has not been in line with its potential. This is associated with several complex and inter-related factors of which inadequate feed is the major one (Osti, 2020). Major feed resources for ruminants in the country include natural pasture, crop stubble, road and riverside pasture, crop residues, and agro-industrial by-products (CSA, 2018). Sheep in the highlands depend on communal grazing, fallow lands and crop residues (Kenfo et al., 2018). These feed resources provide insufficient nutrients beyond maintenance requirements leading to low productivity. This situation is aggravated during the dry season when natural pastures are critically deficient in protein and energy content (Kenfo et al., 2018). Thus, supplementation with high nutritive value feed resources is imperative to improve sheep growth performance and productivity in the country.
Sweet lupine (Lupinus angustifolius L.) is one of the major crops grown in different soil types. Its growth performance compares better than other lupin species (Tessema, 2017) in all locations. It yields 2.98 t/ha of grain in mid altitudes of Southern Ethiopia (Tessema, 2017) and can be used as an alternative home-grown protein supplement to mitigate livestock feed shortages in the country (Haile et al., 2017). It has a relatively high crude protein (CP) content of 34.35%, digestible organic matter (DOM) content of 86.28% and a relatively low alkaloid content (Yenesew et al., 2015). The alkaloid content of sweet lupin was found to be 112 mg/kg DM while the white local varieties has high 10,231 mg/kg DM as reported by Likawent et al. (2012). Besides, a study conducted using sweet lupin grain as a supplement with 290 g/head per day on Washera sheep showed that the animals gained 74 g/head per day and 5.1 kg/head in a trial of 69 days (Yeheyis et al., 2012). Supplementation of sweet lupin has potential to improve the efficiency of utilisation of available roughage feed resources (Rodrigues et al., 2017).
It has been reported by Likawent et al. (2012) that the high alkaloid content of local lupin has negative impact on the utilisation of seeds as livestock and human food.
Soaking after roasting, boiling, germination, fermentation and alkaline treatment are practices that have been reported to reduce anti-nutritional factors in diets (Joray et al., 2007). The practice of processing sweet lupin seed as a supplement for fattening lambs is relatively new in Ethiopia, but it has not been studied. Therefore, this study conducted an on-farm evaluation to determine promising pro-cessing methods of sweet lupin on feed intake, nutrient digestibility and growth performance of Doyogena sheep in Ethiopia.

Farmer selection
The study was undertaken on-farm. The district comprises of 4 urban and 13 rural PA. Ancha Sadicho, one of the rural PA (peasant association -a lower-level administrative hierarchy in Ethiopia), was purposively selected based on availability of sufficient sheep populations as well as willingness and interest of farmers to participate.
Subsequently, 8 volunteer farmers who owned more than 10 sheep were selected from four different villages within the PA (Figure 1).
Selection of the farmers was facilitated by agricultural development agents. Three growing intact male lambs were selected from the flock of each farmer considering uniformity in physical performance, health status and body weight. Before the commencement of the experiment, farmers were trained on experimental procedures.

Experimental feed
Experimental feed consisted of a basal diet of natural grass hay, processed sweet lupin grain and commercial concentrate. The concentrate mix was in proportion of 30% noug seed cake, 35% wheat bran, 34% ground maize grain and 1% salts. Natural pasture hay was obtained from the local market and chopped to 5-15 cm prior to offering. Sweet lupin grain was processed by roasting then grinding, soaking in water for 72 h, or steaming. Roasting was done on a flat plate surface (Mitad) by continuously mixing and stirring the seeds to ensure uniformity and until several black spots were observed on seeds. The temperature of template surface was 144 • C and the average roasting period was 13 min. Roasted grain was, thereafter, ground in an attrition mill. Each kilogram of raw sweet lupin grain was soaked in 2 L of tap water for 72 h. Raw sweet lupin grains were steamed for 30 min.

Experimental design and treatments diets
The experiment was laid down in a randomised complete block design.
Experimental animals were blocked into six groups based on their initial body weight (BW), which was determined after two consecutive weights and taking the average weight for each sheep. Then the sheep were and randomly assigned to one of the four dietary treatments using lottery method for treatments as control, natural pasture hay + concentrate mix (T1), natural pasture + 440 g/day roasted, coarsely ground lupin grain (T2), natural pasture + 440 g/day soaked lupin grains (T3) and natural pasture + 440 g/day steamed lupin grain (T4).

Feeding trial
The experimental sheep were adapted to experimental diets for 15 days and actual data collected for 90 days. Treatment feeds were offered to individual sheep twice daily at 10:00 am and 5:00 pm in equal portions. Refusals were collected, sampled and weighed daily per animal and pooled on treatment basis for laboratory analysis. Daily feed intake of each sheep was recorded. Experimental sheep were weighed on the first day of the feeding trial and subsequently at weekly intervals after overnight fasting.
Feed conversion efficiency (FCE) was calculated as follows: Feed conversion efficiency = Average daily live weight gain (g) Average daily feed intake (g) . (1)

Digestibility trial
The digestibility trial was conducted after 90 days of the feeding trial. It comprised of 3 days for animals to adapt to carrying the faecal collecting bags followed by 7 days of faeces collection. Faeces were collected and weighed every morning for each animal before offering feed and water. It was kept in airtight plastic containers and stored at -20 • C in a deep freezer refrigerator up to completion of the digestibility trial.
Feed offered, and refusals were collected, weighed and recorded every morning. At the end of the digestibility trial, faecal samples were pooled for each sheep, thawed, thoroughly mixed and 20% subsample and dried at 60 • C for 48 h. Faecal samples for determination of dry matter digestibility were air-dried and kept until oven drying at 105 • C. Partially dried faeces were ground to pass through a 1 mm sieve and stored until laboratory analysis.

Chemical analysis
Representative samples of feed offered, refusals, and faecal samples were analysed at the ILRI Animal Nutrition Laboratory in Addis Ababa. Samples of feed offered, refusals and faeces were dried at 60 • C for 48 h in a forced draft oven and ground to pass through 1 mm sieve using a Wiley mill, packed into paper bags and stored pending further laboratory works. They were analysed for dry matter (DM), ash, crude protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin (ADL), in vitro organic matter digestibility (IVOMD) and metabolisable energy (ME) using the sweet lupin near-infrared reflectance spectroscopy (NIRS) prediction equation (Glencross et al., 2008). Prior to scanning using NIRS, ground samples were dried overnight at 60 • C to standardise moisture condi- where DE is digestible energy; IVOMD is in vitro organic matter digestibility; ME is metabolisable energy; MJ is megajoule; mcal is megacalorie; kg is kilogram.

Partial budget analysis
Partial budget analysis was used to determine the profitability of To determine the economic return of the feeding trial, partial budget analysis was calculated according to Upton (1979), as follows: Total return ( To measure the increase in net return associated with each additional unit of expenditure, the marginal rate of return (MRR) was calculated as MRR = NR/TVC.

Statistical analysis
All data from the trial experiments, on feed intake, feed quality (nutritional content of feed) and live weight gain, FCE, and others were summarised and managed with MS-Excel (2010) and then subjected to analysis of variance (ANOVA) in a randomised complete block design using the general linear model procedure of SAS (2002) version 9.00.
Individual differences between means had been tested using Duncan's multiple range test.

Chemical composition of experimental feeds
The result of the chemical composition of the experimental feeds is presented in Table 1. There was higher amount of OM, CP, ME and IVOMD in the conc. mix, RCGSLG, SSLG and StSLG feed components as compared to hay feed, the NDF, ADF and ADL as well as hemicelluloses components of hay were higher than other feed components as shown in the table.

Dry matter and nutrient intake
The DMI of hay in T4 was significantly higher than T1 (

Dry matter and nutrients digestibility
The DM, OM, CP, NDF and ADF digestibility of the lupin groups was significantly higher (p < 0.05) than the control as indicated in Table 3.
There was an improvement of 58

Bodyweight change and feed conversion efficiency
Of the parameters measured related to body weight, the average daily gain and FCE of T4 were significantly higher (p < 0.05) than that of T1 (Table 4). These parameters showed 51.04% and 46.34% increments, respectively, in T4 over the control. However, there was no significant difference between T2 and T3 in the above parameters. BW, body weight of live animal; DMI, dry matter intake; NS, non-signifant; OMI, organic matter intake; NDF, neutral detergent fibre intake; ADF, acid detergent fibre; ADL, acid detergent lignin; CP, crude protein intake; SEM, standard error mean; SL, significant level; T1, concentrate mixture; T2, roasted and coarsely ground sweet lupin grain; T3, soaked sweet lupin grain; T4, steamed sweet lupin grain; ns, non-significant. IBW, initial body weight; FBW, final body weight; BWC, body weight change; ADG, average daily weight gain; FCR, feed conversion efficiency; SEM, standard error of means; NS, non-significant; SL, significance level; kg, kilogram; T1, concentrate mixture; T2, roasted and coarsely ground sweet lupin grain; T3, soaked sweet lupin grain; T4, steamed sweet lupin grain.

Partial budget analysis
Partial budget analysis of Doyogena sheep fed on hay basal diet and supplemented with different forms of processed lupin grain is given in Table 5. All lupin supplemented groups tended to have higher net returns over the control feed sheep groups as shown in the table.

DISCUSSION
It had been stated that CP content ranging between 7% and 7.5% is required to satisfy ruminant microbial demands for nitrogen that would provide sufficient CP for the maintenance requirement of the animals (Van Soest, 1982). The CP content of natural pasture hay in the current finding was lower than the previously reported (Ali et al., 2019) from natural pasture hay but higher than 3.88%, 5.28% and 6.45% reported by Mekuriaw and Asmare (2018), Dejene (2017) and Demoze (2020), respectively, in different parts of Ethiopia. Nevertheless, the observed CP content of natural grass hay used in this on-farm feeding trial was found to be slightly below the maintenance requirements of ruminant animals (sheep). The current CP content in the natural pasture or hay indicates that it requires supplementation with better quality feed to meet not only maintenance requirements but also productivity of animals. On the other hand, the CP content of roasted and coarsely ground sweet lupin grain is high, which enable it to be used to supplement sheep fed poor basal diet. Thus, the use of lupin in the current study is one of the strategies that can mitigate shortage of protein for ruminants in developing countries.

Dry matter and nutrient intake
The total dry matter and nutrient intakes of sheep in the current study improved by supplementation of processed lupin. This is what has been supposed to be obtained in such kinds of studies as the main target of use of protein feeds is to improve the intake of dry matter and nutrients intakes. The dry matter intake normalised for live weight of sheep was not negatively affected by the dietary treatment. That means feeding lupin grains did not affect the palatability of sheep, instead it positively influenced the overall performance of animals. This finding is in agreement with Yilkal et al. (2014) and Yeheyis et al. (2012) reported for supplementation with different forms of processed lupin (Lupinus albus) grain in hay-based feeding of Washera sheep. Moreover, in the current experiment, the different legume and processing methods did not affect the performance of lambs' performances (Lestingi et al., 2019).
On the other hands, Tefera et al. (2015) also reported that supplementation of processed sweet lupin grain improved body weight changes and carcass yield of lambs in Ethiopia. The inconsistency of findings might be related to the types of basal diet used and processing methods of lupin grains in respective studies.

Dry matter and nutrients digestibility
The findings showed an increment in the digestibility of nutrients

Partial budget analysis
The marginal rate of return or ratio for supplemented sheep in T2 and T4 was 3.497 and 53.357ETB (1.10 USD), respectively. The result TA B L E 5 Partial budget and marginal rate of return analysis for Doyogena sheep supplemented with processed sweet lupin grain on hay-based feeding

CONCLUSION
From the current finding, it is understood that steamed lupin grains are more suitable and economical as compared to other types of lupin processing and presumed to be good replacement for commercial concentrate mixed to fattening sheep. The supplements used in this study showed increment in an average daily gain and net return and thus can be used in feeding systems depending on their availability and relative costs. The use of steamed lupin improves the nutritive value of the grain and sheep performance in the current study. For wider use of steamed lupin in the area, the simplification of the steaming process of lupin grains should be studied prior to the final recommendation of this treatment.